In a motorcycle, when excessive back torque is applied from a rear wheel (driving wheel) side to an engine side at shift-down time, the rear wheel is sometimes locked to make the behavior of a vehicle body unstable. Hence, some clutches have a back torque limiter to prevent excessive back torque from being applied from the rear wheel side to the engine side in such a case. The back torque limiter relatively slides a drive plate and a driven plate (establishing a half clutch state) when large back torque is applied, to thereby prevent the rear wheel being locked. However, in a structure in which the half clutch state is always established when large back torque is applied, torque cannot be sufficiently transmitted from the rear wheel to the engine, so that the engine cannot be started, for example, by push starting from a vehicle stop state.
Hence, Patent Literatures 1 and 2 disclose clutches each having a back torque limiter that can reduce back torque during running and transmit the back torque to the engine at the push starting. In the clutch described in Patent Literature 1, a governor plate that switches whether to operate the back torque limiter is provided at a pressure disk that presses a drive plate and a driven plate in an axial direction. Further, in the clutch described in Patent Literature 2, a limiter cancel mechanism that prevents the back torque limiter from operating under a predetermined condition is provided on a tip side of the clutch.
However, in the structure described in Patent Literature 1, a movable component is sandwiched between parts that decide the timing and amount of sliding of the clutch when the back torque limiter operates. Therefore, the structure has a problem of difficult dimension management of components. Further, since the movable component is structured to be provided at the pressure disk, the axial dimension of the clutch increases. On the other hand, the structure described in Patent Literature 2 is a structure in which a lock mechanism is provided at the tip side of the clutch (on a side far from a primary driven gear) and therefore has a problem of a counter shaft being prone to runout.